Handle correctly multiple requires to the same file with different forms

Summary:
The traverse dependencies logic was using the absolute path of the resolved dependency to group the module dependencies, so for example if there's a module like:

```
const a = require('./a');
const a1 = require('./a.js');
```

The traversal dependencies logic was just outputting a single dependency for that module.

Since we're transforming each `require()` call to replace the relative path by a dependencyMap, the code from above was transformed to:

```
const a = require(_dependencyMap[0]);
const a1 = require(_dependencyMap[1]);
```

But since the traverse dependencies logic could only find a single dependency, `_dependencyMap[1]` was undefined, causing a runtime error.

This fixes https://github.com/facebook/metro/issues/152 (more info in the task)

Reviewed By: jeanlauliac

Differential Revision: D7258093

fbshipit-source-id: 65c42b87e589430ecc96b906230dd7c4c55c2146

packages/metro/src/DeltaBundler/__tests__/traverseDependencies-test.js

@@ -366,6 +366,28 @@ describe('edge cases', () => {
     ]);
   });
 
+  it('should create two entries when requiring the same file in different forms', async () => {
+    const edges = new Map();
+    await initialTraverseDependencies('/bundle', dependencyGraph, {}, edges);
+
+    // We're adding a new reference from bundle to foo.
+    Actions.addDependency('/bundle', '/foo', 0, 'foo.js');
+
+    expect(
+      getPaths(
+        await traverseDependencies([...files], dependencyGraph, {}, edges),
+      ),
+    ).toEqual({
+      added: new Set(['/bundle']),
+      deleted: new Set(),
+    });
+
+    expect([...edges.get(entryModule.path).dependencies]).toEqual([
+      ['foo.js', '/foo'],
+      ['foo', '/foo'],
+    ]);
+  });
+
   it('should traverse the dependency tree in a deterministic order', async () => {
     // Mocks the shallow dependency call, always resolving the module in
     // `slowPath` after the module in `fastPath`.

packages/metro/src/DeltaBundler/traverseDependencies.js

@@ -199,7 +199,7 @@ async function processEdge(
   onDependencyAdd: () => mixed,
   onDependencyAdded: () => mixed,
 ): Promise<void> {
-  const previousDependencies = new Set(edge.dependencies.values());
+  const previousDependencies = edge.dependencies;
 
   const result = await dependencyGraph
     .getModuleForPath(edge.path)
@@ -222,12 +222,12 @@ async function processEdge(
   edge.output.source = result.source;
   edge.dependencies = new Map();
 
-  currentDependencies.forEach((relativePath, absolutePath) => {
+  currentDependencies.forEach((absolutePath, relativePath) => {
     edge.dependencies.set(relativePath, absolutePath);
   });
 
-  for (const absolutePath of previousDependencies.values()) {
-    if (!currentDependencies.has(absolutePath)) {
+  for (const [relativePath, absolutePath] of previousDependencies) {
+    if (!currentDependencies.has(relativePath)) {
       removeDependency(edge, absolutePath, edges, delta);
     }
   }
@@ -236,22 +236,24 @@ async function processEdge(
   // added and removed dependency, to get all the modules that have to be added
   // and removed from the dependency graph.
   await Promise.all(
-    Array.from(currentDependencies.keys()).map(async absolutePath => {
-      if (previousDependencies.has(absolutePath)) {
-        return;
-      }
+    Array.from(currentDependencies.entries()).map(
+      async ([relativePath, absolutePath]) => {
+        if (previousDependencies.has(relativePath)) {
+          return;
+        }
 
-      await addDependency(
-        edge,
-        absolutePath,
-        dependencyGraph,
-        transformOptions,
-        edges,
-        delta,
-        onDependencyAdd,
-        onDependencyAdded,
-      );
-    }),
+        await addDependency(
+          edge,
+          absolutePath,
+          dependencyGraph,
+          transformOptions,
+          edges,
+          delta,
+          onDependencyAdd,
+          onDependencyAdded,
+        );
+      },
+    ),
   );
 }
 
@@ -370,12 +372,12 @@ function resolveDependencies(
 
   return new Map(
     dependencies.map(relativePath => [
+      relativePath,
       dependencyGraph.resolveDependency(
         parentModule,
         relativePath,
         transformOptions.platform,
       ).path,
-      relativePath,
     ]),
   );
 }